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Error Identifier: unset.readOnlyProperty

Every error reported by PHPStan has an error identifier. Here’s a list of all error identifiers. In PHPStan Pro you can see the error identifier next to each error and filter errors by their identifiers.

Code example #

<?php declare(strict_types = 1);

class User
{
	public function __construct(
		public readonly string $name,
	)
	{
	}
}

function doFoo(User $user): void
{
	unset($user->name);
}

Why is it reported? #

The unset() call targets a property that is declared as readonly. PHP does not allow unsetting readonly properties outside of the constructor scope. Attempting to do so results in a fatal error at runtime.

This error is also reported for properties marked with @readonly or @immutable PHPDoc tags.

How to fix it #

Remove the unset() call and use a different approach to handle the absence of the value. If the property needs to be nullable, change the type and assign null instead:

 <?php declare(strict_types = 1);
 
 class User
 {
 	public function __construct(
-		public readonly string $name,
+		public readonly ?string $name,
 	)
 	{
 	}
 }

-function doFoo(User $user): void
+function createUser(?string $name): User
 {
-	unset($user->name);
+	return new User($name);
 }

If the property should be mutable, remove the readonly modifier:

 <?php declare(strict_types = 1);
 
 class User
 {
 	public function __construct(
-		public readonly string $name,
+		public string $name,
 	)
 	{
 	}
 }

How to ignore this error #

You can use the identifier unset.readOnlyProperty to ignore this error using a comment:

// @phpstan-ignore unset.readOnlyProperty
codeThatProducesTheError();

You can also use only the identifier key to ignore all errors of the same type in your configuration file in the ignoreErrors parameter:

parameters:
	ignoreErrors:
		-
			identifier: unset.readOnlyProperty

Rules that report this error #

• PHPStan\Rules\Variables\UnsetRule [1]

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